Artificial output reference for model predictive control

ABSTRACT

A control system includes a control module that receives a first request corresponding to a control value for at least one of a plurality of actuators, selectively receives a second request associated with a predicted future control value for at least one of the plurality of actuators, determines a target value for the actuator based on the first request if the second request was not received, and generates a reference signal representing the second request if the second request was received. The reference signal indicates at least one of a predicted increase in the control value and a predicted decrease in the control value. A model predictive control module receives the reference signal and adjusts one of the plurality of actuators associated with the predicted future control value based on the reference signal.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to U.S. patent application Ser. No.14/225,502 filed on Mar. 26, 2014, Ser. No. 14/225,516 filed on Mar. 26,2014, Ser. No. 14/225,569 filed on Mar. 26, 2014, Ser. No. 14/225,626filed on Mar. 26, 2014, Ser. No. 14/225,896 filed on Mar. 26, 2014, Ser.No. 14/225,531 filed on Mar. 26, 2014, Ser. No. 14/225,507 filed on Mar.26, 2014, Ser. No. 14/225,808 filed on Mar. 26, 2014, Ser. No.14/225,587 filed on Mar. 26, 2014, Ser. No. 14/225,492 filed on Mar. 26,2014, Ser. No. 14/226,006 filed on Mar. 26, 2014, Ser. No. 14/226,121filed on Mar. 26, 2014, Ser. No. 14/225,496 filed on Mar. 26, 2014, andSer. No. 14/225,891 filed on Mar. 26, 2014. The entire disclosure of theabove applications are incorporated herein by reference.

FIELD

The present disclosure relates to engine control systems and methods forvehicles.

BACKGROUND

The background description provided here is for the purpose of generallypresenting the context of the disclosure. Work of the presently namedinventors, to the extent it is described in this background section, aswell as aspects of the description that may not otherwise qualify asprior art at the time of filing, are neither expressly nor impliedlyadmitted as prior art against the present disclosure.

Control systems, such as engine control systems, include a plurality ofactuators that are controlled to vary operating parameters. Exampleactuators in an engine control system include, but are not limited to, athrottle valve, spark plug actuators, cam phasers, exhaust gasrecirculation valves, a wastegate, cylinder valves, or any othercomponent for varying engine parameters. The engine control systemcontrols the actuators according to inputs and desired outputs ofvarious systems.

For example, internal combustion engines combust an air and fuel mixturewithin cylinders to drive pistons, which produces drive torque. Air flowinto the engine is regulated via a throttle. More specifically, thethrottle adjusts throttle area, which increases or decreases air flowinto the engine. As the throttle area increases, the air flow into theengine increases. A fuel control system adjusts the rate that fuel isinjected to provide a desired air/fuel mixture to the cylinders and/orto achieve a desired torque output. Increasing the amount of air andfuel provided to the cylinders increases the torque output of theengine.

In spark-ignition engines, spark initiates combustion of an air/fuelmixture provided to the cylinders. In compression-ignition engines,compression in the cylinders combusts the air/fuel mixture provided tothe cylinders. Spark timing and air flow may be the primary mechanismsfor adjusting the torque output of spark-ignition engines, while fuelflow may be the primary mechanism for adjusting the torque output ofcompression-ignition engines.

SUMMARY

A control system includes a control module that receives a first requestcorresponding to a control value for at least one of a plurality ofactuators, selectively receives a second request associated with apredicted future control value for at least one of the plurality ofactuators, determines a target value for the actuator based on the firstrequest if the second request was not received, and generates areference signal indicating the second request if the second request wasreceived. The reference signal indicates at least one of a predictedincrease in the control value and a predicted decrease in the controlvalue. A model predictive control module receives the reference signaland adjusts one of the plurality of actuators associated with thepredicted future control value based on the reference signal.

An engine control system for a vehicle includes a torque requestingmodule that receives at least one torque request, selectively receives apredicted torque reserve request, determines an air torque request basedon the at least one torque request if the predicted torque reserverequest was not received, and generates a torque reference signalindicating the predicted torque reserve request if the predicted torquereserve request was received. The torque reference signal indicates atleast one of a predicted torque request increase and a predicted torquerequest decrease. A model predictive control module receives the torquereference signal and adjusts a torque reserve based on the torquereference signal.

A method of operating an engine control system for a vehicle includesreceiving at least one torque request, selectively receiving a predictedtorque reserve request, determining an air torque request based on theat least one torque request if the predicted torque reserve request wasnot received, generating a torque reference signal indicating thepredicted torque reserve request if the predicted torque reserve requestwas received, wherein the torque reference signal indicates at least oneof a predicted torque request increase and a predicted torque requestdecrease, and adjusting a torque reserve based on the torque referencesignal.

Further areas of applicability of the present disclosure will becomeapparent from the detailed description, the claims and the drawings. Thedetailed description and specific examples are intended for purposes ofillustration only and are not intended to limit the scope of thedisclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will become more fully understood from thedetailed description and the accompanying drawings, wherein:

FIG. 1 is a functional block diagram of an example engine systemaccording to the present disclosure;

FIG. 2 is a functional block diagram of an example engine control systemaccording to the present disclosure;

FIG. 3 is a functional block diagram of an example air control moduleaccording to the present disclosure;

FIG. 4 is a functional block diagram of an example torque requestingmodule according to the present disclosure;

FIGS. 5A and 5B illustrate example timing loops for an artificial torquereference signal according to the present disclosure; and

FIG. 6 is a flow diagram of an example artificial torque referencemethod according to the present disclosure.

In the drawings, reference numbers may be reused to identify similarand/or identical elements.

DETAILED DESCRIPTION

A control module in a control system controls outputs of the systembased on one or more inputs. The control module adjusts variousactuators in the control system to achieve desired operating parametersbased on the inputs. For example, the control module controls theactuators according to respective target values for each of theactuators to achieve the desired operating parameters. The actuatorstypically include some actuators that respond to control relativelyslowly, and some actuators that respond to control relatively slowly.Accordingly, the control system may not be immediately responsive toinputs, and therefore desired outputs (i.e., desired operatingparameters) may be delayed. In other words, the control system may notbe able to immediately achieve the target values for each of theactuators.

A control module according to the present disclosure implements modelpredictive control to generate the target values. More specifically, thecontrol module identifies possible sets of target values based on inputsto the control system. The control module determines predictedparameters for each of the possible sets based on the possible sets'target values and a mathematical model of the system. Further, thecontrol module may selectively generate an artificial reference signalcorresponding to predicted inputs. In this manner, the controls systemcan prepare to control actuators to target values based on the predictedinputs, and therefore more quickly respond when the actual inputs matchthe predicted inputs.

For example only, an engine control module (ECM) controls torque outputof an engine. More specifically, the ECM controls actuators of theengine based on target values, respectively, based on a requested amountof torque. For example, the ECM controls intake and exhaust camshaftphasing based on target intake and exhaust phaser angles, a throttlevalve based on a target throttle opening, an exhaust gas recirculation(EGR) valve based on a target EGR opening, and a wastegate of aturbocharger based on a target wastegate duty cycle.

The ECM could determine the target values individually using multiplesingle input single output (SISO) controllers, such as proportionalintegral derivative (PID) controllers. However, when multiple SISOcontrollers are used, the target values may be set to maintain systemstability at the expense of possible fuel consumption decreases.Additionally, calibration and design of the individual SISO controllersmay be costly and time consuming.

An example ECM that implements the artificial reference signal of thepresent disclosure generates the target values using model predictivecontrol (MPC) as described above, and selectively uses the artificialtorque reference signal to allow for torque reserve management. Morespecifically, the ECM identifies possible sets of target values based onan engine torque request and/or the artificial torque reference signal.The ECM determines predicted parameters for each of the possible setsbased on the possible sets' target values and a mathematical model ofthe engine. For example, the ECM determines a predicted engine outputtorque and a predicted air per cylinder (APC) for each of the possiblesets of target values. The ECM may also determine one or more otherpredicted parameters for each possible set of target values.

The ECM may determine a cost associated with use of each of the possiblesets. For example, the cost of a possible set that is predicted to moreclosely track an engine torque request may be lower than other possiblesets that are not expected to track the engine torque request asclosely. The ECM may select the possible set that has the lowest costand that satisfies various constraints (e.g. to minimize APC) for use tocontrol the actuators. In various implementations, instead of or inaddition to identifying possible sets of target values and determiningthe cost of each of the sets, the ECM may generate a surfacerepresenting the cost of possible sets of target values. The ECM maythen identify the possible set that has the lowest cost based on theslope of the cost surface.

Referring now to FIG. 1, a functional block diagram of an example enginesystem 100 is presented. Although the engine system 100 is presented asan example implementation of the MPC and artificial reference signal,the principles of the present disclosure can be implemented in anycontrol system associated with controlling the target values of one ormore actuators using MPC to achieve desired operating parameters.

The engine system 100 includes an engine 102 that combusts an air/fuelmixture to produce drive torque for a vehicle based on driver input froma driver input module 104. The engine 102 may be a gasoline sparkignition internal combustion engine.

Air is drawn into an intake manifold 110 through a throttle valve 112.For example only, the throttle valve 112 may include a butterfly valvehaving a rotatable blade. An engine control module (ECM) 114 controls athrottle actuator module 116, which regulates opening of the throttlevalve 112 to control the amount of air drawn into the intake manifold110.

Air from the intake manifold 110 is drawn into cylinders of the engine102. While the engine 102 may include multiple cylinders, forillustration purposes a single representative cylinder 118 is shown. Forexample only, the engine 102 may include 2, 3, 4, 5, 6, 8, 10, and/or 12cylinders. The ECM 114 may instruct a cylinder actuator module 120 toselectively deactivate some of the cylinders, which may improve fueleconomy under certain engine operating conditions.

The engine 102 may operate using a four-stroke cycle. The four strokes,described below, may be referred to as the intake stroke, thecompression stroke, the combustion stroke, and the exhaust stroke.During each revolution of a crankshaft (not shown), two of the fourstrokes occur within the cylinder 118. Therefore, two crankshaftrevolutions are necessary for the cylinder 118 to experience all four ofthe strokes.

During the intake stroke, air from the intake manifold 110 is drawn intothe cylinder 118 through an intake valve 122. The ECM 114 controls afuel actuator module 124, which regulates fuel injection to achieve atarget air/fuel ratio. Fuel may be injected into the intake manifold 110at a central location or at multiple locations, such as near the intakevalve 122 of each of the cylinders. In various implementations (notshown), fuel may be injected directly into the cylinders or into mixingchambers associated with the cylinders. The fuel actuator module 124 mayhalt injection of fuel to cylinders that are deactivated.

The injected fuel mixes with air and creates an air/fuel mixture in thecylinder 118. During the compression stroke, a piston (not shown) withinthe cylinder 118 compresses the air/fuel mixture. A spark actuatormodule 126 energizes a spark plug 128 in the cylinder 118 based on asignal from the ECM 114, which ignites the air/fuel mixture. The timingof the spark may be specified relative to the time when the piston is atits topmost position, referred to as top dead center (TDC).

The spark actuator module 126 may be controlled by a timing signalspecifying how far before or after TDC to generate the spark. Becausepiston position is directly related to crankshaft rotation, operation ofthe spark actuator module 126 may be synchronized with crankshaft angle.Generating spark may be referred to as a firing event. The sparkactuator module 126 may have the ability to vary the timing of the sparkfor each firing event. The spark actuator module 126 may vary the sparktiming for a next firing event when the spark timing is changed betweena last firing event and the next firing event. The spark actuator module126 may halt provision of spark to deactivated cylinders.

During the combustion stroke, the combustion of the air/fuel mixturedrives the piston away from TDC, thereby driving the crankshaft. Thecombustion stroke may be defined as the time between the piston reachingTDC and the time at which the piston reaches bottom dead center (BDC).During the exhaust stroke, the piston begins moving away from BDC andexpels the byproducts of combustion through an exhaust valve 130. Thebyproducts of combustion are exhausted from the vehicle via an exhaustsystem 134.

The intake valve 122 may be controlled by an intake camshaft 140, whilethe exhaust valve 130 may be controlled by an exhaust camshaft 142. Invarious implementations, multiple intake camshafts (including the intakecamshaft 140) may control multiple intake valves (including the intakevalve 122) for the cylinder 118 and/or may control the intake valves(including the intake valve 122) of multiple banks of cylinders(including the cylinder 118). Similarly, multiple exhaust camshafts(including the exhaust camshaft 142) may control multiple exhaust valvesfor the cylinder 118 and/or may control exhaust valves (including theexhaust valve 130) for multiple banks of cylinders (including thecylinder 118). In various other implementations, the intake valve 122and/or the exhaust valve 130 may be controlled by devices other thancamshafts, such as camless valve actuators. The cylinder actuator module120 may deactivate the cylinder 118 by disabling opening of the intakevalve 122 and/or the exhaust valve 130.

The time when the intake valve 122 is opened may be varied with respectto piston TDC by an intake cam phaser 148. The time when the exhaustvalve 130 is opened may be varied with respect to piston TDC by anexhaust cam phaser 150. A phaser actuator module 158 may control theintake cam phaser 148 and the exhaust cam phaser 150 based on signalsfrom the ECM 114. When implemented, variable valve lift (not shown) mayalso be controlled by the phaser actuator module 158.

The engine system 100 may include a turbocharger that includes a hotturbine 160-1 that is powered by hot exhaust gases flowing through theexhaust system 134. The turbocharger also includes a cold air compressor160-2 that is driven by the turbine 160-1. The compressor 160-2compresses air leading into the throttle valve 112. In variousimplementations, a supercharger (not shown), driven by the crankshaft,may compress air from the throttle valve 112 and deliver the compressedair to the intake manifold 110.

A wastegate 162 may allow exhaust to bypass the turbine 160-1, therebyreducing the boost (the amount of intake air compression) provided bythe turbocharger. A boost actuator module 164 may control the boost ofthe turbocharger by controlling opening of the wastegate 162. In variousimplementations, two or more turbochargers may be implemented and may becontrolled by the boost actuator module 164.

An air cooler (not shown) may transfer heat from the compressed aircharge to a cooling medium, such as engine coolant or air. An air coolerthat cools the compressed air charge using engine coolant may bereferred to as an intercooler. An air cooler that cools the compressedair charge using air may be referred to as a charge air cooler. Thecompressed air charge may receive heat, for example, via compressionand/or from components of the exhaust system 134. Although shownseparated for purposes of illustration, the turbine 160-1 and thecompressor 160-2 may be attached to each other, placing intake air inclose proximity to hot exhaust.

The engine system 100 may include an exhaust gas recirculation (EGR)valve 170, which selectively redirects exhaust gas back to the intakemanifold 110. The EGR valve 170 may be located upstream of theturbocharger's turbine 160-1. The EGR valve 170 may be controlled by anEGR actuator module 172 based on signals from the ECM 114.

A position of the crankshaft may be measured using a crankshaft positionsensor 180. A rotational speed of the crankshaft (an engine speed) maybe determined based on the crankshaft position. A temperature of theengine coolant may be measured using an engine coolant temperature (ECT)sensor 182. The ECT sensor 182 may be located within the engine 102 orat other locations where the coolant is circulated, such as a radiator(not shown).

A pressure within the intake manifold 110 may be measured using amanifold absolute pressure (MAP) sensor 184. In various implementations,engine vacuum, which is the difference between ambient air pressure andthe pressure within the intake manifold 110, may be measured. A massflow rate of air flowing into the intake manifold 110 may be measuredusing a mass air flow (MAF) sensor 186. In various implementations, theMAF sensor 186 may be located in a housing that also includes thethrottle valve 112.

The throttle actuator module 116 may monitor the position of thethrottle valve 112 using one or more throttle position sensors (TPS)190. An ambient temperature of air being drawn into the engine 102 maybe measured using an intake air temperature (IAT) sensor 192. The enginesystem 100 may also include one or more other sensors 193, such as anambient humidity sensor, one or more knock sensors, a compressor outletpressure sensor and/or a throttle inlet pressure sensor, a wastegateposition sensor, an EGR position sensor, and/or one or more othersuitable sensors. The ECM 114 may use signals from the sensors to makecontrol decisions for the engine system 100.

The ECM 114 may communicate with a transmission control module 194 tocoordinate shifting gears in a transmission (not shown). For example,the ECM 114 may reduce engine torque during a gear shift. The ECM 114may communicate with a hybrid control module 196 to coordinate operationof the engine 102 and an electric motor 198.

The electric motor 198 may also function as a generator, and may be usedto produce electrical energy for use by vehicle electrical systemsand/or for storage in a battery. In various implementations, variousfunctions of the ECM 114, the transmission control module 194, and thehybrid control module 196 may be integrated into one or more modules.

Each system that varies an engine parameter may be referred to as anengine actuator. For example, the throttle actuator module 116 mayadjust opening of the throttle valve 112 to achieve a target throttleopening area. The spark actuator module 126 controls the spark plugs toachieve a target spark timing relative to piston TDC. The fuel actuatormodule 124 controls the fuel injectors to achieve target fuelingparameters. The phaser actuator module 158 may control the intake andexhaust cam phasers 148 and 150 to achieve target intake and exhaust camphaser angles, respectively. The EGR actuator module 172 may control theEGR valve 170 to achieve a target EGR opening area. The boost actuatormodule 164 controls the wastegate 162 to achieve a target wastegateopening area. The cylinder actuator module 120 controls cylinderdeactivation to achieve a target number of activated or deactivatedcylinders.

While the generation of target values using MPC can be implemented tocontrol any of the above actuators (or actuators of any suitable controlsystem), the implementation of the MPC systems and methods according tothe principles of the present disclosure will be described with respectto the ECM 114 for example only. The ECM 114 generates the target valuesfor the engine actuators to cause the engine 102 to generate a targetengine output torque. The ECM 114 generates the target values for theengine actuators using model predictive control, as discussed furtherbelow.

Referring now to FIG. 2, a functional block diagram of an example enginecontrol system is presented. An example implementation of the ECM 114includes a driver torque module 202, an axle torque arbitration module204, and a propulsion torque arbitration module 206. The ECM 114 mayinclude a hybrid optimization module 208. The ECM 114 also includes areserves/loads module 220, a torque requesting module 224, an aircontrol module 228, a spark control module 232, a cylinder controlmodule 236, and a fuel control module 240.

The driver torque module 202 may determine a driver torque request 254based on a driver input 255 from the driver input module 104. The driverinput 255 may be based on, for example, a position of an acceleratorpedal and a position of a brake pedal. The driver input 255 may also bebased on cruise control, which may be an adaptive cruise control systemthat varies vehicle speed to maintain a predetermined followingdistance. The driver torque module 202 may store one or more mappings ofaccelerator pedal position to target torque and may determine the drivertorque request 254 based on a selected one of the mappings.

An axle torque arbitration module 204 arbitrates between the drivertorque request 254 and other axle torque requests 256. Axle torque(torque at the wheels) may be produced by various sources including anengine and/or an electric motor. For example, the axle torque requests256 may include a torque reduction requested by a traction controlsystem when positive wheel slip is detected. Positive wheel slip occurswhen axle torque overcomes friction between the wheels and the roadsurface, and the wheels begin to slip against the road surface. The axletorque requests 256 may also include a torque increase request tocounteract negative wheel slip, where a tire of the vehicle slips in theother direction with respect to the road surface because the axle torqueis negative.

The axle torque requests 256 may also include brake management requestsand vehicle over-speed torque requests. Brake management requests mayreduce axle torque to ensure that the axle torque does not exceed theability of the brakes to hold the vehicle when the vehicle is stopped.Vehicle over-speed torque requests may reduce the axle torque to preventthe vehicle from exceeding a predetermined speed. The axle torquerequests 256 may also be generated by vehicle stability control systems.

The axle torque arbitration module 204 outputs a predicted torquerequest 257 and an immediate torque request 258 based on the results ofarbitrating between the received torque requests 254 and 256. Asdescribed below, the predicted and immediate torque requests 257 and 258from the axle torque arbitration module 204 may selectively be adjustedby other modules of the ECM 114 before being used to control the engineactuators.

In general terms, the immediate torque request 258 may be an amount ofcurrently desired axle torque, while the predicted torque request 257may be an amount of axle torque that may be needed on short notice. TheECM 114 controls the engine system 100 to produce an axle torque equalto the immediate torque request 258. However, different combinations oftarget values may result in the same axle torque. The ECM 114 maytherefore adjust the target values to enable a faster transition to thepredicted torque request 257, while still maintaining the axle torque atthe immediate torque request 258.

In various implementations, the predicted torque request 257 may be setbased on the driver torque request 254. The immediate torque request 258may be set to less than the predicted torque request 257 under somecircumstances, such as when the driver torque request 254 is causingwheel slip on an icy surface. In such a case, a traction control system(not shown) may request a reduction via the immediate torque request258, and the ECM 114 reduces the engine torque output to the immediatetorque request 258. However, the ECM 114 performs the reduction so theengine system 100 can quickly resume producing the predicted torquerequest 257 once the wheel slip stops.

In general terms, the difference between the immediate torque request258 and the (generally higher) predicted torque request 257 can bereferred to as a torque reserve. The torque reserve may represent theamount of additional torque (above the immediate torque request 258)that the engine system 100 can begin to produce with minimal delay. Fastengine actuators are used to increase or decrease current axle torquewith minimal delay. Fast engine actuators are defined in contrast withslow engine actuators.

In general terms, fast engine actuators can change the axle torque morequickly than slow engine actuators. Slow actuators may respond moreslowly to changes in their respective target values than fast actuatorsdo. For example, a slow actuator may include mechanical components thatrequire time to move from one position to another in response to achange in target value. A slow actuator may also be characterized by theamount of time it takes for the axle torque to begin to change once theslow actuator begins to implement the changed target value. Generally,this amount of time will be longer for slow actuators than for fastactuators. In addition, even after beginning to change, the axle torquemay take longer to fully respond to a change in a slow actuator.

For example only, the spark actuator module 126 may be a fast actuator.Spark-ignition engines may combust fuels including, for example,gasoline and ethanol, by applying a spark. By way of contrast, thethrottle actuator module 116 may be a slow actuator.

For example, as described above, the spark actuator module 126 can varythe spark timing for a next firing event when the spark timing ischanged between a last firing event and the next firing event. By way ofcontrast, changes in throttle opening take longer to affect engineoutput torque. The throttle actuator module 116 changes the throttleopening by adjusting the angle of the blade of the throttle valve 112.Therefore, when the target value for opening of the throttle valve 112is changed, there is a mechanical delay as the throttle valve 112 movesfrom its previous position to a new position in response to the change.In addition, air flow changes based on the throttle opening are subjectto air transport delays in the intake manifold 110. Further, increasedair flow in the intake manifold 110 is not realized as an increase inengine output torque until the cylinder 118 receives additional air inthe next intake stroke, compresses the additional air, and commences thecombustion stroke.

Using these actuators as an example, a torque reserve can be created bysetting the throttle opening to a value that would allow the engine 102to produce the predicted torque request 257. Meanwhile, the spark timingcan be set based on the immediate torque request 258, which is less thanthe predicted torque request 257. Although the throttle openinggenerates enough air flow for the engine 102 to produce the predictedtorque request 257, the spark timing is retarded (which reduces torque)based on the immediate torque request 258. The engine output torque willtherefore be equal to the immediate torque request 258.

When additional torque is needed, the spark timing can be set based onthe predicted torque request 257 or a torque between the predicted andimmediate torque requests 257 and 258. By the following firing event,the spark actuator module 126 may return the spark timing to an optimumvalue, which allows the engine 102 to produce the full engine outputtorque achievable with the air flow already present. The engine outputtorque may therefore be quickly increased to the predicted torquerequest 257 without experiencing delays from changing the throttleopening.

The axle torque arbitration module 204 may output the predicted torquerequest 257 and the immediate torque request 258 to a propulsion torquearbitration module 206. In various implementations, the axle torquearbitration module 204 may output the predicted and immediate torquerequests 257 and 258 to the hybrid optimization module 208.

The hybrid optimization module 208 may determine how much torque shouldbe produced by the engine 102 and how much torque should be produced bythe electric motor 198. The hybrid optimization module 208 then outputsmodified predicted and immediate torque requests 259 and 260,respectively, to the propulsion torque arbitration module 206. Invarious implementations, the hybrid optimization module 208 may beimplemented in the hybrid control module 196.

The predicted and immediate torque requests received by the propulsiontorque arbitration module 206 are converted from an axle torque domain(torque at the wheels) into a propulsion torque domain (torque at thecrankshaft). This conversion may occur before, after, as part of, or inplace of the hybrid optimization module 208.

The propulsion torque arbitration module 206 arbitrates betweenpropulsion torque requests 290, including the converted predicted andimmediate torque requests. The propulsion torque arbitration module 206generates an arbitrated predicted torque request 261 and an arbitratedimmediate torque request 262. The arbitrated torque requests 261 and 262may be generated by selecting a winning request from among receivedtorque requests. Alternatively or additionally, the arbitrated torquerequests may be generated by modifying one of the received requestsbased on another one or more of the received torque requests.

For example, the propulsion torque requests 290 may include torquereductions for engine over-speed protection, torque increases for stallprevention, and torque reductions requested by the transmission controlmodule 194 to accommodate gear shifts. The propulsion torque requests290 may also result from clutch fuel cutoff, which reduces the engineoutput torque when the driver depresses the clutch pedal in a manualtransmission vehicle to prevent a flare in engine speed.

The propulsion torque requests 290 may also include an engine shutoffrequest, which may be initiated when a critical fault is detected. Forexample only, critical faults may include detection of vehicle theft, astuck starter motor, electronic throttle control problems, andunexpected torque increases. In various implementations, when an engineshutoff request is present, arbitration selects the engine shutoffrequest as the winning request. When the engine shutoff request ispresent, the propulsion torque arbitration module 206 may output zero asthe arbitrated predicted and immediate torque requests 261 and 262.

In various implementations, an engine shutoff request may simply shutdown the engine 102 separately from the arbitration process. Thepropulsion torque arbitration module 206 may still receive the engineshutoff request so that, for example, appropriate data can be fed backto other torque requestors. For example, all other torque requestors maybe informed that they have lost arbitration.

The reserves/loads module 220 receives the arbitrated predicted andimmediate torque requests 261 and 262. The reserves/loads module 220 mayadjust the arbitrated predicted and immediate torque requests 261 and262 to create a torque reserve and/or to compensate for one or moreloads. The reserves/loads module 220 then outputs adjusted predicted andimmediate torque requests 263 and 264 to the torque requesting module224.

For example only, a catalyst light-off process or a cold start emissionsreduction process may require retarded spark timing. The reserves/loadsmodule 220 may therefore increase the adjusted predicted torque request263 above the adjusted immediate torque request 264 to create retardedspark for the cold start emissions reduction process. In anotherexample, the air/fuel ratio of the engine and/or the mass air flow maybe directly varied, such as by diagnostic intrusive equivalence ratiotesting and/or new engine purging. Before beginning these processes, atorque reserve may be created or increased to quickly offset decreasesin engine output torque that result from leaning the air/fuel mixtureduring these processes.

The reserves/loads module 220 may also create or increase a torquereserve in anticipation of a future load, such as power steering pumpoperation or engagement of an air conditioning (A/C) compressor clutch.The reserve for engagement of the A/C compressor clutch may be createdwhen the driver first requests air conditioning. The reserves/loadsmodule 220 may increase the adjusted predicted torque request 263 whileleaving the adjusted immediate torque request 264 unchanged to producethe torque reserve. Then, when the A/C compressor clutch engages, thereserves/loads module 220 may increase the adjusted immediate torquerequest 264 by the estimated load of the A/C compressor clutch.

The torque requesting module 224 receives the adjusted predicted andimmediate torque requests 263 and 264. The torque requesting module 224determines how the adjusted predicted and immediate torque requests 263and 264 will be achieved. The torque requesting module 224 may be enginetype specific. For example, the torque requesting module 224 may beimplemented differently or use different control schemes forspark-ignition engines versus compression-ignition engines.

In various implementations, the torque requesting module 224 may definea boundary between modules that are common across all engine types andmodules that are engine type specific. For example, engine types mayinclude spark-ignition and compression-ignition. Modules prior to thetorque requesting module 224, such as the propulsion torque arbitrationmodule 206, may be common across engine types, while the torquerequesting module 224 and subsequent modules may be engine typespecific.

The torque requesting module 224 determines an air torque request 265based on the adjusted predicted and immediate torque requests 263 and264. The air torque request 265 may be a brake torque. Brake torque mayrefer to torque at the crankshaft under the current operatingconditions.

Target values for airflow controlling engine actuators are determinedbased on the air torque request 265. More specifically, based on the airtorque request 265, the air control module 228 determines a targetwastegate opening area 266, a target throttle opening area 267, a targetEGR opening area 268, a target intake cam phaser angle 269, and a targetexhaust cam phaser angle 270. The air control module 228 determines thetarget wastegate opening area 266, the target throttle opening area 267,the target EGR opening area 268, the target intake cam phaser angle 269,and the target exhaust cam phaser angle 270 using model predictivecontrol, as discussed further below.

The boost actuator module 164 controls the wastegate 162 to achieve thetarget wastegate opening area 266. For example, a first conversionmodule 272 may convert the target wastegate opening area 266 into atarget duty cycle 274 to be applied to the wastegate 162, and the boostactuator module 164 may apply a signal to the wastegate 162 based on thetarget duty cycle 274. In various implementations, the first conversionmodule 272 may convert the target wastegate opening area 266 into atarget wastegate position (not shown), and convert the target wastegateposition into the target duty cycle 274.

The throttle actuator module 116 controls the throttle valve 112 toachieve the target throttle opening area 267. For example, a secondconversion module 276 may convert the target throttle opening area 267into a target duty cycle 278 to be applied to the throttle valve 112,and the throttle actuator module 116 may apply a signal to the throttlevalve 112 based on the target duty cycle 278. In variousimplementations, the second conversion module 276 may convert the targetthrottle opening area 267 into a target throttle position (not shown),and convert the target throttle position into the target duty cycle 278.

The EGR actuator module 172 controls the EGR valve 170 to achieve thetarget EGR opening area 268. For example, a third conversion module 280may convert the target EGR opening area 268 into a target duty cycle 282to be applied to the EGR valve 170, and the EGR actuator module 172 mayapply a signal to the EGR valve 170 based on the target duty cycle 282.In various implementations, the third conversion module 280 may convertthe target EGR opening area 268 into a target EGR position (not shown),and convert the target EGR position into the target duty cycle 282.

The phaser actuator module 158 controls the intake cam phaser 148 toachieve the target intake cam phaser angle 269. The phaser actuatormodule 158 also controls the exhaust cam phaser 150 to achieve thetarget exhaust cam phaser angle 270. In various implementations, afourth conversion module (not shown) may be included and may convert thetarget intake and exhaust cam phaser angles into target intake andexhaust duty cycles, respectively. The phaser actuator module 158 mayapply the target intake and exhaust duty cycles to the intake andexhaust cam phasers 148 and 150, respectively. In variousimplementations, the air control module 228 may determine a targetoverlap factor and a target effective displacement, and the phaseractuator module 158 may control the intake and exhaust cam phasers 148and 150 to achieve the target overlap factor and the target effectivedisplacement.

The torque requesting module 224 may also generate a spark torquerequest 283, a cylinder shut-off torque request 284, and a fuel torquerequest 285 based on the predicted and immediate torque requests 263 and264. The spark control module 232 may determine how much to retard thespark timing (which reduces engine output torque) from an optimum sparktiming based on the spark torque request 283. For example only, a torquerelationship may be inverted to solve for a target spark timing 286. Fora given torque request (T_(Req)), the target spark timing (S_(T)) 286may be determined based on:S _(T) =f ⁻¹(T _(Req),APC,I,E,AF,OT,#),  (1)where APC is an APC, I is an intake valve phasing value, E is an exhaustvalve phasing value, AF is an air/fuel ratio, OT is an oil temperature,and # is a number of activated cylinders. This relationship may beembodied as an equation and/or as a lookup table. The air/fuel ratio(AF) may be the actual air/fuel ratio, as reported by the fuel controlmodule 240.

When the spark timing is set to the optimum spark timing, the resultingtorque may be as close to a minimum spark advance for best torque (MBT)as possible. MBT corresponds to a maximum engine output torque that isgenerated for a given air flow as spark timing is advanced, while usingfuel having an octane rating greater than a predetermined octane ratingand using stoichiometric fueling. The spark timing at which this maximumtorque occurs is referred to as an MBT spark timing. The optimum sparktiming may differ slightly from MBT spark timing because of, forexample, fuel quality (such as when lower octane fuel is used) andenvironmental factors, such as ambient humidity and temperature. Theengine output torque at the optimum spark timing may therefore be lessthan MBT. For example only, a table of optimum spark timingscorresponding to different engine operating conditions may be determinedduring a calibration phase of vehicle design, and the optimum value isdetermined from the table based on current engine operating conditions.

The cylinder shut-off torque request 284 may be used by the cylindercontrol module 236 to determine a target number of cylinders todeactivate 287. In various implementations, a target number of cylindersto activate may be used. The cylinder actuator module 120 selectivelyactivates and deactivates the valves of cylinders based on the targetnumber 287.

The cylinder control module 236 may also instruct the fuel controlmodule 240 to stop providing fuel for deactivated cylinders and mayinstruct the spark control module 232 to stop providing spark fordeactivated cylinders. The spark control module 232 may stop providingspark to a cylinder once an fuel/air mixture that is already present inthe cylinder has been combusted.

The fuel control module 240 may vary the amount of fuel provided to eachcylinder based on the fuel torque request 285. More specifically, thefuel control module 240 may generate target fueling parameters 288 basedon the fuel torque request 285. The target fueling parameters 288 mayinclude, for example, target mass of fuel, target injection startingtiming, and target number of fuel injections.

During normal operation, the fuel control module 240 may operate in anair lead mode in which the fuel control module 240 attempts to maintaina stoichiometric air/fuel ratio by controlling fueling based on airflow. For example, the fuel control module 240 may determine a targetfuel mass that will yield stoichiometric combustion when combined with apresent mass of air per cylinder (APC).

The torque requesting module 224 selectively outputs an artificialtorque reference signal 292 according to the present disclosure insteadof the air torque request 265. The torque reference signal 292 maycorrespond to a predicted load request and may be based on predictedtorque reserve/load requests 294, including, but not limited to, thereserve/load requests provided to the reserves/loads module 220. Forexample, the predicted reserve/load requests 294 may be based onindications of future torque request changes received from thetransmission control module 194, air conditioning requests, or any otherrequests requiring a future change in torque. If the torque requestingmodule 224 determines that one or more of the predicted reserve/loadrequests 294 will require an increased or decreased amount of reservetorque, the torque requesting module 224 may output the artificialtorque reference signal 292 instead of the air torque request 265. Inthis manner, the air control module 228 controls one or more of thetarget values 266-270 according to the artificial torque referencesignal to be able to more quickly meet torque reserve demands when theair torque request 265 subsequently increases/decreases to match theartificial torque reference signal 292.

FIG. 3 is a functional block diagram of an example implementation of theair control module 228. Referring now to FIGS. 2 and 3, as discussedabove, the air torque request 265 may be a brake torque. A torqueconversion module 304 converts the air torque request 265 from braketorque into base torque. The torque request resulting from conversioninto base torque will be referred to as a base air torque request 308.Alternatively, the torque conversion module 304 receives the artificialtorque reference signal 292 and converts the artificial torque referencesignal 292 into the base air torque request 308.

Base torques may refer to torque at the crankshaft made during operationof the engine 102 on a dynamometer while the engine 102 is warm and notorque loads are imposed on the engine 102 by accessories, such as analternator and the A/C compressor. The torque conversion module 304 mayconvert the air torque request 265 or the artificial torque referencesignal 292 into the base air torque request 308, for example, using amapping or a function that relates brake torques to base torques. Invarious implementations, the torque conversion module 304 may convertthe air torque request 265 or the artificial torque reference signal 292into another suitable type of torque, such as an indicated torque. Anindicated torque may refer to a torque at the crankshaft attributable towork produced via combustion within the cylinders.

An MPC module 312 generates the target values 266-270 using a MPC (ModelPredictive Control) scheme. The MPC module 312 may be a single module ormay comprise multiple modules. For example, the MPC module 312 mayinclude a sequence determination module 316. The sequence determinationmodule 316 determines possible sequences of the target values 266-270that could be used together during N future control loops.

A prediction module 323 determines predicted responses of the engine 102to the possible sequences of the target values 266-270, respectively,based on a (mathematical) model 324 of the engine 102, exogenous inputs328, and feedback inputs 330. More specifically, based on a possiblesequence of the target values 266-270, the exogenous inputs 328, and thefeedback inputs 330, using the model 324, the prediction module 323generates a sequence of predicted torques of the engine 102 for the Ncontrol loops, a sequence of predicted APCs for the N control loops, asequence of predicted amounts of external dilution for the N controlloops, a sequence of predicted amounts of residual dilution for the Ncontrol loops, a sequence of predicted combustion phasing values for theN control loops, and a sequence of predicted combustion quality valuesfor the N control loops.

The model 324 may be, for example, a function or a mapping calibratedbased on characteristics of the engine 102. Dilution may refer to anamount of exhaust from a prior combustion event trapped within acylinder for a combustion event. External dilution may refer to exhaustprovided for a combustion event via the EGR valve 170. Residual dilution(also referred to as internal dilution) may refer to exhaust thatremains in a cylinder and/or exhaust that is pushed back into thecylinder following the exhaust stroke of a combustion cycle.

Combustion phasing may refer to a crankshaft position where apredetermined amount of fuel injected is combusted within a cylinderrelative to a predetermined crankshaft position for combustion of thepredetermined amount of injected fuel. For example, combustion phasingmay be expressed in terms of CA50 relative to a predetermined CA50. CA50may refer to a crankshaft angle (CA) where 50 percent of a mass ofinjected fuel has been combusted within a cylinder. The predeterminedCA50 may correspond to a CA50 where a maximum amount of work is producedfrom the fuel injected and may be approximately 8.5-approximately 10degrees after TDC (top dead center) in various implementations. Whilecombustion phasing will be discussed in terms of CA50 values, anothersuitable parameter indicative of combustion phasing may be used.Additionally, while combustion quality will be discussed as coefficientof variation (COV) of indicated mean effective pressure (IMEP) values,another suitable parameter indicative of combustion quality may be used.

The exogenous inputs 328 may include parameters that are not directlyaffected by the throttle valve 112, the EGR valve 170, the turbocharger,the intake cam phaser 148, and the exhaust cam phaser 150. For example,the exogenous inputs 328 may include engine speed, turbocharger inletair pressure, IAT, and/or one or more other parameters. The feedbackinputs 330 may include, for example, an estimated torque output of theengine 102, an exhaust pressure downstream of the turbine 160-1 of theturbocharger, the IAT, an APC of the engine 102, an estimated residualdilution, an estimated external dilution, and/or one or more othersuitable parameters. The feedback inputs 330 may be measured usingsensors (e.g., the IAT) and/or estimated based on one or more otherparameters.

Each of the possible sequences identified by the sequence determinationmodule 316 includes one sequence of N values for each of the targetvalues 266-270. In other words, each possible sequence includes asequence of N values for the target wastegate opening area 266, asequence of N values for the target throttle opening area 267, asequence of N values for the target EGR opening area 268, a sequence ofN values for the target intake cam phaser angle 269, and a sequence of Nvalues for the target exhaust cam phaser angle 270. Each of the N valuesare for a corresponding one of the N future control loops. N is aninteger greater than or equal to one.

A cost module 332 determines a cost value for each of the possiblesequences of the target values 266-270 based on the predicted parametersdetermined for a possible sequence and output reference values 356. Anexample cost determination is discussed further below.

A selection module 344 selects one of the possible sequences of thetarget values 266-270 based on the costs of the possible sequences,respectively. For example, the selection module 344 may select the oneof the possible sequences having the lowest cost while satisfyingactuator constraints 348 and output constraints 352.

In various implementations, satisfaction of the actuator constraints 348and the output constraints may be considered in the cost determination.In other words, the cost module 332 may determine the cost valuesfurther based on the actuator constraints 348 and the output constraints352. As discussed further below, based on how the cost values aredetermined, the selection module 344 will select the one of the possiblesequences that best achieves the base air torque request 208 whileminimizing the APC, subject to the actuator constraints 348 and theoutput constraints 352.

The selection module 344 may set the target values 266-270 to the firstones of the N values of the selected possible sequence, respectively. Inother words, the selection module 344 may set the target wastegateopening area 266 to the first one of the N values in the sequence of Nvalues for the target wastegate opening area 266, set the targetthrottle opening area 267 to the first one of the N values in thesequence of N values for the target throttle opening area 267, set thetarget EGR opening area 268 to the first one of the N values in thesequence of N values for the target EGR opening area 268, set the targetintake cam phaser angle 269 to the first one of the N values in thesequence of N values for the target intake cam phaser angle 269, and setthe target exhaust cam phaser angle 270 to the first one of the N valuesin the sequence of N values for the target exhaust cam phaser angle 270.

During a next control loop, the MPC module 312 identifies possiblesequences, generates the predicted parameters for the possiblesequences, determines the cost of each of the possible sequences,selects of one of the possible sequences, and sets of the target values266-270 to the first set of the target values 266-270 in the selectedpossible sequence. This process continues for each control loop.

An actuator constraint module 360 (see FIG. 2) sets one of the actuatorconstraints 348 for each of the target values 266-270. In other words,the actuator constraint module 360 sets an actuator constraint for thethrottle valve 112, an actuator constraint for the EGR valve 170, anactuator constraint for the wastegate 162, an actuator constraint forthe intake cam phaser 148, and an actuator constraint for the exhaustcam phaser 150.

The actuator constraints 348 for each one of the target values 266-270may include a maximum value for an associated target value and a minimumvalue for that target value. The actuator constraint module 360 maygenerally set the actuator constraints 348 to predetermined operationalranges for the associated actuators. More specifically, the actuatorconstraint module 360 may generally set the actuator constraints 348 topredetermined operational ranges for the throttle valve 112, the EGRvalve 170, the wastegate 162, the intake cam phaser 148, and the exhaustcam phaser 150, respectively.

However, the actuator constraint module 360 may selectively adjust oneor more of the actuator constraints 348 under some circumstances. Forexample, the actuator constraint module 360 may adjust the actuatorconstraints for a given actuator to narrow the operational range forthat engine actuator when a fault is diagnosed in that engine actuator.For another example only, the actuator constraint module 360 may adjustthe actuator constraints such that the target value for a given actuatorfollows a predetermined schedule over time or changes by a predeterminedamount, for example, for a fault diagnostic, such as a cam phaser faultdiagnostic, a throttle diagnostic, an EGR diagnostic, etc. For a targetvalue to follow a predetermined schedule over time or to change by apredetermined amount, the actuator constraint module 360 may set theminimum and maximum values to the same value. The minimum and maximumvalues being set to the same value may force the corresponding targetvalue to be set to the same value as the minimum and maximum values. Theactuator constraint module 360 may vary the same value to which theminimum and maximum values are set over time to cause the target valueto follow a predetermined schedule.

An output constraint module 364 (see FIG. 2) sets the output constraints352 for the predicted torque output of the engine 102, the predictedCA50, the predicted COV of IMEP, the predicted residual dilution, andthe predicted external dilution. The output constraints 352 for each oneof the predicted values may include a maximum value for an associatedpredicted parameter and a minimum value for that predicted parameter.For example, the output constraints 352 may include a minimum torque, amaximum torque, a minimum CA50 and a maximum CA50, a minimum COV of IMEPand a maximum COV of IMEP, a minimum residual dilution and a maximumresidual dilution, and a minimum external dilution and a maximumexternal dilution.

The output constraint module 364 may generally set the outputconstraints 352 to predetermined ranges for the associated predictedparameters, respectively. However, the output constraint module 364 mayvary one or more of the output constraints 352 under some circumstances.For example, the output constraint module 364 may retard the maximumCA50, such as when knock occurs within the engine 102. For anotherexample, the output constraint module 364 may increase the maximum COVof IMEP under low load conditions, such as during engine idling wherethe a higher COV of IMEP may be needed to achieve a given torquerequest.

A reference module 368 (see FIG. 2) generates the reference values 356for the target values 266-270, respectively. The reference values 356include a reference for each of the target values 266-270. In otherwords, the reference values 356 include a reference wastegate openingarea, a reference throttle opening area, a reference EGR opening area, areference intake cam phaser angle, and a reference exhaust cam phaserangle.

The reference module 368 may determine the reference values 356, forexample, based on the air torque request 265, the base air torquerequest 308, and/or one or more other suitable parameters. The referencevalues 356 provide references for setting the target values 266-270,respectively. The reference values 356 may be used to determine the costvalues for possible sequences. The reference values 356 may also be usedfor one or more other reasons, such as by the sequence determinationmodule 316 to determine possible sequences.

Instead of or in addition to generating sequences of possible targetvalues and determining the cost of each of the sequences, the MPC module312 may identify a sequence of possible target values having the lowestcost using convex optimization techniques. For example, the MPC module312 may determine the target values 266-270 using a quadraticprogramming (QP) solver, such as a Dantzig QP solver. In anotherexample, the MPC module 312 may generate a surface of cost values forthe possible sequences of the target values 266-270 and, based on theslope of the cost surface, identify a set of possible target valueshaving the lowest cost. The MPC module 312 may then test that set ofpossible target values to determine whether that set of possible targetvalues will satisfy the actuator constraints 348 and the outputconstraints 352. The MPC module 312 selects the set of possible targetvalues having the lowest cost while satisfying the actuator constraints348 and the output constraints 352.

The cost module 332 may determine the cost for the possible sequences ofthe target values 266-270 based on relationships between: the predictedtorque and the base air torque request 308; the predicted APC and zero;the possible target values and the respective actuator constraints 348;the other predicted parameters and the respective output constraints352; and the possible target values and the respective reference values356. The relationships may be weighted, for example, to control theeffect that each of the relationships has on the cost.

For example only, the cost module 332 may determine the cost for apossible sequence of the target values 266-270 based on the equation:Cost=Σ_(i=1) ^(N) wT*∥TP _(i)−BATR∥+wA*∥APCP_(i)−0∥,where Cost is the cost for the possible sequence of the target values266-270, TPi is the predicted torque of the engine 102 for an i-th oneof the N control loops, BATR is the base air torque request 308, and wTis a weighting value associated with the relationship between thepredicted and reference engine torques. APCPi is a predicted APC for thei-th one of the N control loops and wA is a weighting value associatedwith the relationship between the predicted APC and zero.

The cost module 332 may determine the cost for a possible sequence ofthe target values 266-270 based on the following more detailed equation:Cost=Σ_(i=1) ^(N)ρε² +wT ²*∥TP_(i)−BATR∥² +wA ²*∥APCP_(i)−0∥² +wTV²*∥PTTOi−TORef∥² +wWG ²*∥PTWGOi−EGORef∥² +wEGR²*∥PTEGROi−EGRORef∥² +wIP²*∥PTICPi−ICPRef∥² +wEP ²*∥PTECPi−ECPRef∥²,subject to the actuator constraints 348 and the output constraints 352.Cost is the cost for the possible sequence of the target values 266-270,TPi is the predicted torque of the engine 102 for an i-th one of the Ncontrol loops, BATR is the base air torque request 308, and wT is aweighting value associated with the relationship between the predictedand reference engine torques. APCPi is a predicted APC for the i-th oneof the N control loops and WA is a weighting value associated with therelationship between the predicted APC and zero.

PTTOi is a possible target throttle opening for the i-th one of the Ncontrol loops, TORef is the reference throttle opening, and wTV is aweighting value associated with the relationship between the possibletarget throttle openings and the reference throttle opening. PTWGOi is apossible target wastegate opening for the i-th one of the N controlloops, WGORef is the reference wastegate opening, and wWG is a weightingvalue associated with the relationship between the possible targetwastegate openings and the reference wastegate opening.

PTEGROi is a possible target EGR opening for the i-th one of the Ncontrol loops, EGRRef is the reference EGR opening, and wEGR is aweighting value associated with the relationship between the possibletarget EGR openings and the reference EGR opening. PTICi is a possibletarget intake cam phaser angle for the i-th one of the N control loops,ICPRef is the reference intake cam phaser angle, and wIP is a weightingvalue associated with the relationship between the possible targetintake cam phaser angle and the reference intake cam phaser angle. PTECiis a possible target exhaust cam phaser angle for the i-th one of the Ncontrol loops, ECPRef is the reference exhaust cam phaser angle, and wEPis a weighting value associated with the relationship between thepossible target exhaust cam phaser angle and the reference exhaust camphaser angle.

ρ is a weighting value associated with satisfaction of the outputconstraints 352. ε is a variable that the cost module 332 may set basedon whether the output constraints 352 will be satisfied. For example,the cost module 332 may increase ε when a predicted parameter is greaterthan or less than the corresponding minimum or maximum value (e.g., byat least a predetermined amount). The cost module 332 may set ε to zerowhen all of the output constraints 352 are satisfied. ρ may be greaterthan the weighting value wT, the weighting value wA, and the otherweighting values (wTV, wWG, wEGR, wIP, wEP) such that the costdetermined for a possible sequence will be large if one or more of theoutput constraints 352 are not satisfied. This may help preventselection of a possible sequence where one or more of the outputconstraints 352 are not satisfied.

The weighting value wT may be greater than the weighting value wA andthe weighting values wTV, wWG, wEGR, wIP, and wEP. In this manner, therelationship between the relationship between the predicted enginetorque and the base air torque request 308 have a larger effect on thecost and, therefore, the selection of one of the possible sequences asdiscussed further below. The cost increases as the difference betweenthe predicted engine torque and the base air torque request 308increases and vice versa.

The weighting value wA may be less than the weighting value wT andgreater than the weighting values wTV, wWG, wEGR, wIP, and wEP. In thismanner, the relationship between the predicted APC and zero has a largeeffect on the cost, but less than the relationship between the predictedengine torque and the base air torque request 308. The cost increases asthe difference between the predicted APC and zero increases and viceversa. While the example use of zero is shown and has been discussed, apredetermined minimum APC may be used in place of zero.

Determining the cost based on the difference between the predicted APCand zero therefore helps ensure that the APC will be minimized.Decreasing APC decreases fuel consumption as fueling is controlled basedon the actual APC to achieve a target air/fuel mixture. As the selectionmodule 344 may select the one of the possible sequences having thelowest cost, the selection module 344 may select the one of the possiblesequences that best achieves the base air torque request 308 whileminimizing the APC.

The weighting values wTV, wWG, wEGR, wIP, and wEP may be less than allof the other weighting values. In this manner, during steady-stateoperation, the target values 266-270 may settle near or at the referencevalues 356, respectively. During transient operation, however, the MPCmodule 312 may adjust the target values 266-270 away from the referencevalues 356 in order to achieve the base air torque request 308, whileminimizing the APC and satisfying the actuator constraints 348 and theoutput constraints 352.

In operation, the MPC module 312 may determine the cost values for thepossible sequences. The MPC module 312 may then select the one of thepossible sequences having the lowest cost. The MPC module 312 may nextdetermine whether the selected possible sequence satisfies the actuatorconstraints 348. If so, the possible sequence may be used. If not, theMPC module 312 determines, based on the selected possible sequence, apossible sequence that satisfies the actuator constraints 348 and thathas the lowest cost. The MPC module 312 may use the possible sequencethat satisfies the actuator constraints 348 and that has the lowestcost.

Referring now to FIG. 4, an example torque requesting module 400according to the present disclosure includes a torque request outputmodule 404 and an artificial torque reference module 408. The torquerequest output module 404 receives the predicted and immediate torquerequests 263 and 264 and the predicted reserve/load requests 294 andselectively outputs one of the air torque request 265 and the artificialtorque reference signal 292 accordingly. For example, if the torquerequesting module 400 does not receive any of the predicted reserve/loadrequests 294 (and/or none of the predicted reserve/load requests 294indicate a needed future change in torque reserve due to a transmissionshift, air conditioning increase, etc.), then the torque request outputmodule 404 may output the air torque request 265 based on the predictedand immediate torque requests 263 and 264.

Conversely, if the torque requesting module 400 receives predictedreserve/load requests 294 indicating a future torque request/reservechange, then the torque request output module 404 instead outputs theartificial torque reference signal 292. For example, the torque requestoutput module 404 may calculate the artificial torque reference signal292 based on the predicted and immediate torque requests 263 and 264 andthe predicted reserve/load requests 294.

Alternatively, the torque request output module 404 may retrieve a valuefor the artificial torque reference signal 292 from the artificialtorque reference module 408. For example, the artificial torquereference module 408 may calculate (e.g., model) the artificial torquereference signal 292 based on the predicted and immediate torquerequests 263 and 264, the predicted reserve/load requests 294, types ofthe predicted reserve/load requests, etc., which may be provided to theartificial torque reference module 408 by the torque request outputmodule 404. In some implementations, the artificial torque referencemodule 408 may store a plurality of values for the artificial torquereference signal 292 indexed by the predicted and immediate torquerequests 263 and 264 and the predicted reserve/load requests 294 (e.g.,in a lookup table). The values for the artificial torque referencesignal 292 may include offsets (e.g., positive or negative offsets to beadded to or subtracted from a value calculated for the air torquerequest 265.

Accordingly, the artificial torque reference signal 292 may correspondto a value calculated for the air torque request 265, plus or minus anoffset corresponding to one or more of the predicted reserve/loadrequests 294. In this manner, the artificial torque reference signal 292includes the air torque request 265 and any anticipated future changesto the air torque request 265 indicated by one or more of the predictedreserve/load requests 294.

Referring now to FIGS. 5A and 5B, example timing loops 500-1 through500-7 (referred to collectively as timing loops 500) illustrate anartificial torque reference signals 504 (artificial torque referencesignals 504-1 through 504-7) provided to the model predictive controlmodule 312 (e.g., via the torque conversion module 304 and the base airtorque request 308).

In each one of the timing loops 500, the respective artificial torquereference signal 504 corresponds to a requested torque profile providedto the model predictive control module 312 at a given time (0, +1, +2, .. . , +6), and indicates predicted requested torque for one or more timesteps 508 in the future. For example, for each of the timing loops 500,“1” indicates a first time step in the future (e.g., 25 ms after therespective artificial torque reference signal 504 is provided to themodel predictive control module 312), “2” indicates a second time stepin the future, “3” indicates a third time step in the future, etc.

For example, in the timing loop 500-1, the signal 504-1 indicates anincrease in predicted requested torque at the third time step 3.Accordingly, the model predictive control module 312 can begin toincrease torque reserve 512 in anticipation of the increase in thepredicted requested torque at the third time step 3 as indicated by theartificial torque reference signal 504-1. Consequently, the torquereserve 512 will increase at the first time step 1, the second time step2, and the third time step 3 until the torque reserve 512 is sufficientto compensate for the predicted requested torque in the third time step3. However, an actual requested torque 516 is not changed at the firsttime step 1 or the second time step 2 because the model predictivecontrol module 312 does not need to provide the increased torque untilthe third time step 3. In this manner, the model predictive controlmodule 312 prepares for the increase in requested torque indicated bythe artificial torque reference signal 504-1 at the third time step 3 byincreasing the torque reserve 512 without affecting the actual requestedtorque 516.

In the timing loops 500-2, 500-3, and 500-4, the signals 504-2, 504-3,and 504-4, respectively, again indicate an increase in predictedrequested torque at the third time step 3. Accordingly, the torquereserve 512 continues to increase in anticipation of the predicted(i.e., scheduled) increase in requested torque indicated by the signal504 at the third time step 3. The artificial torque reference signal 504may be provided with the future increase indicated at the third timestep 3 in the future until the torque reserve 512 is approximatelysufficient to compensate for the increase (i.e., approximately equal tothe additional torque required when the actual requested torque 512increases to match the artificial torque reference signal 514) as shownin the timing loop 500-4.

In the timing loop 500-5, the artificial torque reference signal 514-5indicates the increase in predicted requested torque at the second timestep 2. In the timing loop 500-6, the artificial torque reference signal514-6 indicates the increase in predicted requested torque at the firsttime step 1. Accordingly, the torque reserve 512 is maintained at alevel sufficient to compensate for the increase in predicted requestedtorque. In the timing loop 500-7, the actual requested torque 516increases to match the artificial torque reference signal 514-7.However, because the model predictive torque module 312 previouslyprepared for the increase, the torque reserve 512 is immediatelyavailable. As shown in the timing loop 500-7, the torque reserve 512 isquickly depleted in response to the increase in actual requested torque516.

Although the predicted requested torque is shown in FIGS. 5A and 5B asan increase, the predicted requested torque may also correspond to adecrease in requested torque. Accordingly, the model predictive controlmodule 312 can anticipate a decrease in requested torque (e.g., bydecreasing torque reserve).

In this manner, a future torque request (i.e., as indicated by thepredicted torque request) can be repeated a same number of time stepsfrom the current time step in successive timing loops until the torquereserve 512 is sufficiently prepared to accommodate the future torquerequest. When the torque reserve 512 is sufficiently prepared, theactual torque request change is provided to the MPC module 312.

Referring now to FIG. 6, an example artificial torque reference method600 begins at 604. At 608, the method 600 receives predicted andimmediate torque requests. At 612, the method 600 determines whether anypredicted reserve/load requests were received. If true, the method 600continues to 616. If false, the method 600 continues to 620. At 620, themethod 600 generates an air torque request based on the predicted andimmediate torque requests. At 624, the method 600 controls torquereserve based on the air torque request. The method 600 ends at 628.

At 616, the method 600 determines an artificial torque request signalbased on the predicted and immediate torque requests, the predictedreserve request, and/or an air torque request. At 632, the method 600controls reserve torque based on the artificial torque reference signal.

The foregoing description is merely illustrative in nature and is in noway intended to limit the disclosure, its application, or uses. Thebroad teachings of the disclosure can be implemented in a variety offorms. Therefore, while this disclosure includes particular examples,the true scope of the disclosure should not be so limited since othermodifications will become apparent upon a study of the drawings, thespecification, and the following claims. As used herein, the phrase atleast one of A, B, and C should be construed to mean a logical (A or Bor C), using a non-exclusive logical OR. It should be understood thatone or more steps within a method may be executed in different order (orconcurrently) without altering the principles of the present disclosure.

In this application, including the definitions below, the term modulemay be replaced with the term circuit. The term module may refer to, bepart of, or include an Application Specific Integrated Circuit (ASIC); adigital, analog, or mixed analog/digital discrete circuit; a digital,analog, or mixed analog/digital integrated circuit; a combinationallogic circuit; a field programmable gate array (FPGA); a processor(shared, dedicated, or group) that executes code; memory (shared,dedicated, or group) that stores code executed by a processor; othersuitable hardware components that provide the described functionality;or a combination of some or all of the above, such as in asystem-on-chip.

The term code, as used above, may include software, firmware, and/ormicrocode, and may refer to programs, routines, functions, classes,and/or objects. The term shared processor encompasses a single processorthat executes some or all code from multiple modules. The term groupprocessor encompasses a processor that, in combination with additionalprocessors, executes some or all code from one or more modules. The termshared memory encompasses a single memory that stores some or all codefrom multiple modules. The term group memory encompasses a memory that,in combination with additional memories, stores some or all code fromone or more modules. The term memory may be a subset of the termcomputer-readable medium. The term computer-readable medium does notencompass transitory electrical and electromagnetic signals propagatingthrough a medium, and may therefore be considered tangible andnon-transitory. Non-limiting examples of a non-transitory tangiblecomputer readable medium include nonvolatile memory, volatile memory,magnetic storage, and optical storage.

The apparatuses and methods described in this application may bepartially or fully implemented by one or more computer programs executedby one or more processors. The computer programs includeprocessor-executable instructions that are stored on at least onenon-transitory tangible computer readable medium. The computer programsmay also include and/or rely on stored data.

What is claimed is:
 1. A control system, comprising: a control modulethat receives a first request corresponding to a control value for atleast one of a plurality of actuators, selectively receives a secondrequest associated with a predicted future control value for at leastone of the plurality of actuators, if the second request was notreceived, determines a target value for the actuator based on the firstrequest, and if the second request was received, generates a referencesignal representing the second request, wherein the reference signalindicates at least one of a predicted increase in the control value anda predicted decrease in the control value; and a model predictivecontrol module that receives the reference signal and adjusts one of theplurality of actuators associated with the predicted future controlvalue based on the reference signal.
 2. The control system of claim 1,wherein the reference signal corresponds to the first request plus orminus an offset indicated by the second request.
 3. The control systemof claim 1, wherein control module determines the reference signal basedon the first request and the second request.
 4. The control system ofclaim 1, wherein the reference signal includes an increase at a secondtime subsequent to a first time that the reference signal is provided tothe model predictive control module.
 5. The control system of claim 4,wherein the model predictive control module adjusts the one of theplurality of actuators associated with the predicted future controlvalue prior to the second time.
 6. An engine control system for avehicle, the engine control system comprising: a torque requestingmodule that receives at least one torque request and selectivelyreceives a predicted torque reserve request, if the predicted torquereserve request was not received, determines an air torque request basedon the at least one torque request, and if the predicted torque reserverequest was received, generates a torque reference signal indicating thepredicted torque reserve request, wherein the torque reference signalindicates at least one of a predicted torque request increase and apredicted torque request decrease; and a model predictive control modulethat receives the torque reference signal and adjusts a torque reservebased on the torque reference signal.
 7. The engine control system ofclaim 6, wherein the torque reference signal corresponds to the airtorque request plus or minus an offset indicated by the predicted torquereserve request.
 8. The engine control system of claim 6, wherein thetorque requesting module determines the torque reference signal based onthe at least one torque request and the predicted torque reserverequest.
 9. The engine control system of claim 6, wherein the torquereference signal includes an increase at a second time subsequent to afirst time that the torque reference signal is provided to the modelpredictive control module.
 10. The engine control system of claim 9,wherein the model predictive control module increases the torque reserveprior to the second time.
 11. The engine control system of claim 10,wherein the model predictive control module increases the torque reserveuntil the torque reserve is approximately equal to an amount of torquecorresponding to the predicted torque reserve request.
 12. The enginecontrol system of claim 11, wherein the torque reference signal includesthe increase at a third time subsequent to the first time when thetorque reserve is approximately equal to an amount of torquecorresponding to the predicted torque reserve request, and wherein thethird time is subsequent to the first time and prior to the second time.13. A method of operating an engine control system for a vehicle, themethod comprising: receiving at least one torque request, selectivelyreceiving a predicted torque reserve request; determining an air torquerequest based on the at least one torque request if the predicted torquereserve request was not received; determining a torque reference signalindicating the predicted torque reserve request if the predicted torquereserve request was received, wherein the torque reference signalindicates at least one of a predicted torque request increase and apredicted torque request decrease; and adjusting a torque reserve basedon the torque reference signal.
 14. The method of claim 13, wherein thetorque reference signal corresponds to the air torque request plus orminus an offset indicated by the predicted torque reserve request. 15.The method of claim 13, further comprising determining the torquereference signal based on the at least one torque request and thepredicted torque reserve request.
 16. The method of claim 13, whereinthe torque reference signal includes an increase at a second timesubsequent to a first time that the torque reference signal isdetermined.
 17. The method of claim 16, further comprising increasingthe torque reserve prior to the second time.
 18. The method of claim 17,further comprising increasing the torque reserve until the torquereserve is approximately equal to an amount of torque corresponding tothe predicted torque reserve request.
 19. The method of claim 18,wherein the torque reference signal includes the increase at a thirdtime subsequent to the first time when the torque reserve isapproximately equal to an amount of torque corresponding to thepredicted torque reserve request, and wherein the third time issubsequent to the first time and prior to the second time.